From 2f221d6f7b881d95de1f356a3097d755ab1e47d4 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 21 Jan 2021 14:19:26 +0100 Subject: attr: handle idmapped mounts When file attributes are changed most filesystems rely on the setattr_prepare(), setattr_copy(), and notify_change() helpers for initialization and permission checking. Let them handle idmapped mounts. If the inode is accessed through an idmapped mount map it into the mount's user namespace. Afterwards the checks are identical to non-idmapped mounts. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Helpers that perform checks on the ia_uid and ia_gid fields in struct iattr assume that ia_uid and ia_gid are intended values and have already been mapped correctly at the userspace-kernelspace boundary as we already do today. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Link: https://lore.kernel.org/r/20210121131959.646623-8-christian.brauner@ubuntu.com Cc: Christoph Hellwig Cc: David Howells Cc: Al Viro Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner --- fs/overlayfs/copy_up.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'fs/overlayfs/copy_up.c') diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c index e5b616c93e11..3e9957ae19fa 100644 --- a/fs/overlayfs/copy_up.c +++ b/fs/overlayfs/copy_up.c @@ -235,7 +235,7 @@ static int ovl_set_size(struct dentry *upperdentry, struct kstat *stat) .ia_size = stat->size, }; - return notify_change(upperdentry, &attr, NULL); + return notify_change(&init_user_ns, upperdentry, &attr, NULL); } static int ovl_set_timestamps(struct dentry *upperdentry, struct kstat *stat) @@ -247,7 +247,7 @@ static int ovl_set_timestamps(struct dentry *upperdentry, struct kstat *stat) .ia_mtime = stat->mtime, }; - return notify_change(upperdentry, &attr, NULL); + return notify_change(&init_user_ns, upperdentry, &attr, NULL); } int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat) @@ -259,7 +259,7 @@ int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat) .ia_valid = ATTR_MODE, .ia_mode = stat->mode, }; - err = notify_change(upperdentry, &attr, NULL); + err = notify_change(&init_user_ns, upperdentry, &attr, NULL); } if (!err) { struct iattr attr = { @@ -267,7 +267,7 @@ int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat) .ia_uid = stat->uid, .ia_gid = stat->gid, }; - err = notify_change(upperdentry, &attr, NULL); + err = notify_change(&init_user_ns, upperdentry, &attr, NULL); } if (!err) ovl_set_timestamps(upperdentry, stat); -- cgit From c7c7a1a18af4c3bb7749d33e3df3acdf0a95bbb5 Mon Sep 17 00:00:00 2001 From: Tycho Andersen Date: Thu, 21 Jan 2021 14:19:28 +0100 Subject: xattr: handle idmapped mounts When interacting with extended attributes the vfs verifies that the caller is privileged over the inode with which the extended attribute is associated. For posix access and posix default extended attributes a uid or gid can be stored on-disk. Let the functions handle posix extended attributes on idmapped mounts. If the inode is accessed through an idmapped mount we need to map it according to the mount's user namespace. Afterwards the checks are identical to non-idmapped mounts. This has no effect for e.g. security xattrs since they don't store uids or gids and don't perform permission checks on them like posix acls do. Link: https://lore.kernel.org/r/20210121131959.646623-10-christian.brauner@ubuntu.com Cc: Christoph Hellwig Cc: David Howells Cc: Al Viro Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig Reviewed-by: James Morris Signed-off-by: Tycho Andersen Signed-off-by: Christian Brauner --- fs/overlayfs/copy_up.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) (limited to 'fs/overlayfs/copy_up.c') diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c index 3e9957ae19fa..f81b836c2256 100644 --- a/fs/overlayfs/copy_up.c +++ b/fs/overlayfs/copy_up.c @@ -85,9 +85,9 @@ int ovl_copy_xattr(struct super_block *sb, struct dentry *old, if (ovl_is_private_xattr(sb, name)) continue; retry: - size = vfs_getxattr(old, name, value, value_size); + size = vfs_getxattr(&init_user_ns, old, name, value, value_size); if (size == -ERANGE) - size = vfs_getxattr(old, name, NULL, 0); + size = vfs_getxattr(&init_user_ns, old, name, NULL, 0); if (size < 0) { error = size; @@ -114,7 +114,7 @@ retry: error = 0; continue; /* Discard */ } - error = vfs_setxattr(new, name, value, size, 0); + error = vfs_setxattr(&init_user_ns, new, name, value, size, 0); if (error) { if (error != -EOPNOTSUPP || ovl_must_copy_xattr(name)) break; @@ -795,7 +795,7 @@ static ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value) ssize_t res; char *buf; - res = vfs_getxattr(dentry, name, NULL, 0); + res = vfs_getxattr(&init_user_ns, dentry, name, NULL, 0); if (res == -ENODATA || res == -EOPNOTSUPP) res = 0; @@ -804,7 +804,7 @@ static ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value) if (!buf) return -ENOMEM; - res = vfs_getxattr(dentry, name, buf, res); + res = vfs_getxattr(&init_user_ns, dentry, name, buf, res); if (res < 0) kfree(buf); else @@ -846,8 +846,8 @@ static int ovl_copy_up_meta_inode_data(struct ovl_copy_up_ctx *c) * don't want that to happen for normal copy-up operation. */ if (capability) { - err = vfs_setxattr(upperpath.dentry, XATTR_NAME_CAPS, - capability, cap_size, 0); + err = vfs_setxattr(&init_user_ns, upperpath.dentry, + XATTR_NAME_CAPS, capability, cap_size, 0); if (err) goto out_free; } -- cgit